Telephone-exchange system.



J. L. WRIGHT.

TELEPHONE EXQHANGE SYSTEM. APPLICATION HLED'OCT. e. 1914.

l g'mfim. Patented Aug. 6, 1918.

3 SHEETSSHEET I.

V/Z f Mai? of /AM@ W J. L. WRIGHT.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED OCT. 6, IBM.

Patented Aug. 6, 1918,

3 SHEETSSHEE]' 2.

W$IVESSE6T Ma J. L. WRIGHT.

TELEPHONE EXCHANGESYSTEM.

APPLICATION FILED OCT. 6 I914.

Patented Aug. 6, 1918.

3 SHEETS-SHEET 3.

WITNESSES.-

"UNITED STATES PATENT oFFioE.

JOSEPH L. WRIGHT, OF CLEVELAND, OHIO, ASSIGNOR TO WESTERN ELECTRICCOMPANY, INCORPORATED, A CORPORATION OF NEW YORK.

Specification of Letters Patent.

Patented Aug. 6, 1918.

Application filed October 6, 1914. Serial No. 865,261.

To all whom it may concern:

Be it known that I, JOSEPH L'. WRIGHT, a citizen of the United States,residing at Cleveland, in the county of Cuyahoga and State of Ohio, haveinvented certain new and useful Improvements in Telephone-ExchangeSystems, of which the following is a specification.

My invention relates to telephone ex-' change systems employingautomatic switching mechanism for interconnecting subscribersv lines. Myinvention is applicable to such systems whether of the full automatic orsemi-automatic types.

The manner in which the switches are controlled allows two-wire ormetallic circuits to be used. In systems employing such circuits forcontrolling the automatic switches it has been customary to employ acombination of slow and quick acting relays. The quick acting relays areresponsive to rapid makes and breaks in the metallic circuits caused bythe sending devices and in turn. transmit these impulses to the controlmagnets of the automatic switches to cause them to assume apiedetermined position. The slow acting relays act in response tocurrent changes of long duration produced at the sending devices andshift the various circuits at the automatic switches and serve tocontrol their release.

With my invention no slow acting relays or retarded devices are used.The impulses from the sending devices which are produced by simplymaking and breaking the metallic circuit operate designating devicesassociated with the automatic switches at the central oflice,

Each automatic switch is provided with its individual stepping oractuating circuit After such contacts are rendered selectable theautomatic switches travel at their own speed and after selecting theactive conpredetermined individual contact in the group to be selected.

In the present instance I have shown my invention applied to a system ofthe full automatic type, but, of course, it can be equally well appliedto systems of the semiautomatic type.

For illustration I have shown in detail the designating means asconsisting of a group of step-by-step relays. Relays of this characterand for selective purposes are shown in Patent No. 965,976 to J. L.Wright; of August- 2. 1910.

I My invention is illustrated in the accompanying drawings, wherein:

Figure 1 shows a subscribers line equipment.

Fig. 2 shows a first selector switch and its associated designatingdevice.

Fig. 3 shows a connector switch and its associated designating device.Fig, 4 showst-he Wiring of the designating cont-acts associated with aconnector switch.

Fig. 5 shows a modified form of designat ng. means consisting of astep-by-step switch.

Referring to Fig. 1, the subscribers station AA is equipped withapparatus usual in common battery systems and in addition is providedwith a sending device. In the present instance I have designated this(le vice by means of a push button *0. The operation of the sendingdevice serves to open and close the line conductors and so causeimpulses to be transmitted to control the automatic switches.

The first selector switch J (Fig. 2) is of the two-motion type. It firstrotates to select the proper group of contacts and then steps,vertically to select a particular contact in the group. The row wiper 33sweeps over the row designating contacts while the switch is rotatingand when an active contact is engaged, the rotary action of the switchis arrested and it then steps in a vertical direction.

The designating device consists of the step-by-step relays marked K,1-K, etc., and L, 1-L, etc. In the present instance I have shown butfive sets of these relays,

and, consequently, have shown but five row designating contacts inassociation therewith. In practice, however, there would be ten rowdesignating contacts such as shown in Fig. 4:. In providing ten contactsthere would, of course, be ten sets of step-by-step relays.

The designating relays are controlled by relay A, whichrespondsto-impulses transmitted at the subscribers station.

Fig. 3 shows a connector switch X and its associated set of designatingrelays R, 1R, etc., and S, 1S,- etc. In the present instance I haveshown but three sets of designated relays and three sets of row and 1ndividual designating contacts assoc1ated with the switch X. In practice,however, there would be ten sets of contacts and ten sets of designatingrelays.

The designating contacts in the connector switch X are arranged andconnected in accordance with Fig. 4. No. 1 row contact is connected inmultiple with No. 1 individual contact of each row or group. The samearrangement is made in connection-with the remaining row and individualcontacts. These row and individual contacts are rendered active orselectable by the same set of designating relays.

The switch X like switch J also first rotates and then steps in avertical direction.

Fig. 5 shows how designating contacts are rendered selectable by meansof a step-bystep switch 500. The magnet'50l of this switch responds tothe impulses caused by the sending device and engages a particularcontact in the bank of a selector or connector switch, as the case maybe. As soon as the designating contact is selected by the selectorswitch, relay 5M is operated and closes the circuit of the releasemagnet 6-M, thereby causing the switch 500 to. restore.

The details of the various circuits can best be understood by describingthe operation of the apparatus in tracing a call from a calling to acalled subscriber. For illustration we will assume that subscriber atstation AA desires to'converse with a subscriber whose number is 32-1.

The subscriber at station AA removes his receiver and then operates thesending device circuit and causes theoperation of relay A.

springs 40, 26, winding of relay C to battery B. Relay C after operatingremains locked to ground through the back contacts of relay M. Theoperation of relay C connects battery to the locking contacts of the setof relays L, 1L, etc., and K, 1K and also connects battery to a contactof relay A.

The subscriber at AA in operating his sending device causes ,relay A torespond and transmit impulses to the set of designating relays. Duringthe first impulse when relay A restores, the circuit of relay L iscompleted by the following path: battery B, contacts of relay C, 9,contacts of relay A, 10, contacts of relay K, 11, winding of relay L toground. The operation of relay L places relay K in condition tobeoperated at the next energization of relay A by the following path;battery B, contacts of relay C, 9, contacts of relay A, 12, contacts ofrelay L, 13, contacts of relay 1L, 14, winding of relay K to ground. Theoperation of relay K connects ground to No. 1 row contact of the switchJ by the following path: ground, contacts of relay etK, 3K, 2K, 1-K andK. The operation of relay K also completes the circuit of the rotarymagnet E of the switch J by the following path: ground, contacts ofrelay K, 29, winding of magnet E, 30, contactsof relay F to battery B,

The next impulse transmitted at the substation causes relays 1L and 1Kto be operated and the operation of the latter relay causes ground to beconnected to No. 2 row contact of the switch J and to be removed fromNo. 1 contact. The next impulse at the substation causes relays 2L and2K to be operated, and the operation of the latter relay causes groundto be disconnected from No. 2 contact but connected to No. 3 contact.

It will be noticed that the operation of relay K completes the circuitof the rotary magnet E. Theoperation of this magnet causes the switch Jto step in a rotary direction. At each operation of the magnet E therelay F has its circuit completed by contacts associated with the magnetand in operating opens the circuit of the magnet. This coiiperationbetween the relay and the magnet causes a vibrating effect and thevibration of the magnet E causes the switch J to step accordingly.

The impulses, however, which are transmitted at the substation are at afaster rate orin advance of the stepping of the switch J controlled bythe magnet E, and, consequently, the ground connections to the variousrow contacts are always shifted in advance of the row wiper After thefirst set of impulses have been transmitted, however, and which in thepresent instancearc three in number. there is an interval caused for thenext set of impulses. During this interval the wiper 33 engages No. 3contact which was grounded by the operation of relay 2K. As soon asconnection is effected with this contact the circuit of relay M iscompleted and it in operating remains locked to ground through contactsof the release magnet H of the switch J. The operation of relay Mremoves ground from the locking contact of relay C and this relay inrestorin removes battery from the locking contacts 0' the set ofdesignating relays. These relays which were energized by thetransmission of three impulses from the substation restore and therestoration of relay K opens the circuit of magnet E, causing the switchJ to come to rest with its wipers 34, 35 and 36 in line with the properrow or group of contacts leading to connector switches.

The operation of relay M completes the circuit of the test relay D ofthe switch J by the following path: ground, contacts of relay M, camsprlngs 45, winding of rela D to battery B. The operation of relaycompletes the circuit of the vertical stepping magnet G of the switch J.This magnet in operating closesits associated contact springs andoperates relay F, and this relay in operating opens the circuit of themagnet itself. This action between the relay and the magnet causes avibrating efiect and the operation of the magnet causes the switch J tostep vertically until relay D restores. This relay restores when thetest wiper 34 engages an idlecontact leading to a connector switch. Assoon as such a contact is found relay D restores, thereby opening thecircuit of the magnet G and causing the switch J to come to rest andengage contacts leading to an idle connector switch. The restoration ofrelay D completes the circuit of the cut-0E relay N by the followingpath: ground, contact of relays D and M, 23, winding of relay N tobattery B. The operation of relay N removes battery and ground re-.

spectively from the windings of relay A and the coil I.

From the foregoing it will be noticed that as soon as connection iseffected with an idle trunk, the battery supply relay and coil are Whenthe first'selector switch J engagescontacts leading to an idle connectorswitch,

relay Y has its'circuit completed as follows I battery B, resistancecoil 100, winding of relay Y, test contacts34, contacts of relay D, 7,winding of magnet H to ground. Re lay Y is of low resistance, but isadjusted to operate in series with the winding of the coil 100 and thewinding of the magnet H. The magnet H, however, is so adjusted that itwill not operate in series with the winding of the relay Y and the coil100, but it will, however, operate in series with the winding o'f-relayY alone. ,In addition to relay Y becoming energized as soon as theconnector switch is selected, relay 1A will also be operated as it hasits winding connected directly to the tip conductor and supplies batteryto the calling line while the coil 1I supplies ground to the otherconductor eX- tending to the calling line. The operation of relay 1Acompletes the circuit of the locking relay lC by the following path:ground, contacts of relay 1A, 77, winding of relay 1G, 76, contacts ofrelay 4M to battery B. I The operation of relay l-C connects battery tothe contact of relay 1A which controls the operation of the set of Irelays R, 1R, etc., and S, 1S, etc.

The subscriber at station AA operating his sending device the secondtime causes two impulses to be transmitted, thereby operating relay 1Aaccordingly. Relay 1A restoring during the transmission of the firstimpulse completes the circuit of relay S by the following path: battery,contacts of relay 1- C, 64, contacts of relay 1A, 201, contacts of relayR, 69, winding of relay S to ground. The operation of relay 1-Afollowing the transmission of the first impulse completes the circuit ofrelay R by the following path: battery, contacts of relay 1C, 64,contacts of relay 1A, 65, contacts of relay S, 66, contacts of relay1-S, 67, wind- .of the switch X by the following path:

ground, contacts of relay 4-M, contacts of relay R, contacts of relay2M, 97, winding of magnet U, 98, contacts of relay V to battery B.

The operation of magnet U causesits associated contact springs to beclosed, thereby operating relay V, which in turn opens the circuit ofthe magnet U. This action causes a vibrating efl'ect between the magnet"and relay and the operation of the former causes the switch X torotate. As'soon as the row wiper 1 10 engages No. 2 contact. which '13.grounded, then relay 1-M-is operated. The operation of this relaydisconnects battery from the locking contacts-of relays S, 1S,

R and 1R, thereby causing them to restore. The restoration of relay Ropens the circuit for controlling the stepping magnets of the switch X.The operation of relay 1M also completes the circuit of relay 2-M by thefollowing path: ground, contacts of relay 1-M, 70, winding of relay 2Mto battery B. The operation of this relay disconnects the rotary magnetU and in its place connects the vertical magnet W.

From the foregoing it will be noted that after the second group ofimpulses have been transmitted and the'designated row has beenselectedby the row wiper 110 then the designating relays are releasedand the circuit of the "ertical magnet WV substituted for that of therotary magnet U.

The subscriber at station AA transmitting one impulse operates relay lAaccordingly, which in turn causes the operation of relays S and R. Theoperation of relay B connects ground to No. 1,.contact in the designatedrow, and also completes the circuit of the vertical magnet 1V of theswitch X. The operation of the magnet W causes the switch X to stepvertically and when the wiper 115 engages No. 1 contact, which isgrounded, then relay 3M has its circuit completed and in operatingcompletes the circuit of relay 1M. The operation of this relay (t-M)opens the circuit of the vertical magnet W of the switch X, causing thewipers to rest on contacts leading to the called-for line.

In case the called-for line is busy then the test relay 0 will beoperated by current flowing over the following path: ground, testcontacts of the called line, test wiper 105, contacts of relay 3-M,winding of relay 0 to battery B.

The operation of relay 0 completes the circuit of the release magnet P,thereby causing the restoration of the switch X. The operation of thisrelay also connects a suitable busy tone test "to the trunk conductornotifying the calling subscriber that the called-for line is busy. Therelay 0 remains locked to ground through the contacts of relay Y. RelayY is deenergized when the calling subscriber replaces his receiver andit in restoring releases relay 0.

In case the called-for line is not busy then relay 0 will not beaffected. The operation of relay 4M completes the circuit of relay T,the action of which closes the tip and sleeve conductors and completesthe circuit between the calling and 'called subscribers lines. Thecircuit of the cut-oil relay of the called-for line, which correspondsto relay N of Fig. 2, is operated by the following path: ground,contacts of relay 1C, (which was restored by the action of relay 4=M)107, contacts of relay 3M, 106, test wiper 105 to the winding of cut-oilrelay N to battery B. The operation of this latter relay disconnectsbattery from' the relay A and ground from the coil I, thus clearing thetip and sleeve conductors of the called-for line The operation of relay4-M completes arness the circuit of the ringing relay Z. This latterrelay is operated intermittently by the commutator 200 and when operatedconnects generator current to the called-for line.

When the called subscriber removes his receiver in response to the call,tip relay Q isoperated. The operation of this relay opens the lockingcircuit of relay 2M and this latter relay in restoring opens the circuitof ringing relay Z.

At the termination of the conversation, the called subscriber replacinghis receiver causes relay Q to restore. The restoration of this relaycompletes the circuit of the release magnet P by the following path:ground, cam springs 101, 72, back contacts of relay Q, 71, back contactsof relays 2M and l- -C, 74, winding of magnet P to battery B. Theoperation of this magnet causes the switch X to restore to its normalposition. The switch in reaching its normal position opens cam springs101, thereby causing relay 4-M to restore.

The calling subscriber replacing his receiver causes relay 1A torestore. This relay in restoring connects battery between the winding ofrelay Y and the coil 100 by the followin path: battery B, contacts ofrelay 1- 62, contacts of relay Y to the winding of coil 100 and thewinding of relay Y. The effect. of battery being applied in this mannershunts the coil 100, thereby allowing the release magnet H of the firstselector switch J to be operated. The operation of this magnet H causesthe restoration of the switch J and also removes ground from the lockingcontact of relay M causing it to restore. The restoration of switch Jremoves ground from the winding of relay Y, thereby allowing it torestore, and it in restoring removes the shunt from coil 100.

In case the calling subscriber replaces his receiver first, the firstselector switch J is released in the manner previously described and thecalled subscriber retains control of the connector switch X. If,however, the called subscriber does not respond then the connectorswitch X, as well as the first connector switch J, is under control ofthe calling subscriber. In the latter event the release of the switch Xis efiected by the circuit of the release magnet P being operated by thefollowing path: ground, cam springs 101, 72, contacts of relay Q, 71,contacts of relay 1A, 73, contacts of relay'1-C, 74, winding of magnet Pto battery B.

Referring to Fig. 4, it will be noted that the last set of designatingcontacts are shown connected to ound. This ground connection is provi edin case the calling subscriber should start the operation of theapparatus and then re lace his receiver before connection isestablished. Relay L (Fig. 2) is shown provided with an armature whichcontrols the starting circuit for stepping magnet E of the switch J. Theconnection is shown in dotted lines in multiple with the connections onrelay K. The same provision is made i connection with the connectorswitch.(F1g. 3) as relay S is provided with a set of contacts connectedin multiple to si .iar contacts on relay R.

In case the calling subscriber should remove his receiver and then failto operate his sending device relay C (Fi 2) would be operated as wellas relay L. elay C is operated at the energization of relay A and relayL operated at the denergization of relay A. In such an event relay Lbeing operated would complete the circuit of the rotary magnet E andcause-the switch J to rotate until the wiper 33 engages the permanentlygrounded designating contact. As soon as this contact is engaged relay Moperates in the manner previously described and the switch J will thenautomatically select an idle switch. As soon as such a switch isselected the release magnetH would be operated in series with thewinding of relay Y as relay 1-A would be deenergized as the receiver ofthe calling subscriber is replaced.

I [and thereby operate relay S. Relay S would complete the startingcircuit for stepping magnets of the switch X and this switch wouldrotate until the last row of designating contacts, which is grounded, isreached. After this operation the switch X would then step verticallyuntil the last designating contact in the row is engaged, whereuponrelay 3-'M would become energized and operate relay 4-M. The operationof this latter relay would restore'relay 1C-, thereby allowing relay Yand, the release magnet H to be placed in series and the operation ofthe magnet would cause the switch J to restore. The restoration of relay1C also allows the circuit of the release magnet P of the switch X to becompleted.

From the foregoing it will be noted that after the tip relay of aselector or a connector switch is operated and should the callingsubscriber replace his receiver the initial starting circuits for theswitches is completed and they will step just as though the subscriberhad actually operated his sending device.

The designating devices,,whether consisting of step-by-step relays orstep-by-step switches should respond to impulses delivered at a fasterrate of speed than the stepping of the main switches. The speed of the.main switches can be controlled by proper adjustments or.other meanswell known 1n the art. Instead of depending entirely upon combinationwith an automatic switch and a control circuit therefor, of meansindividually associated with said switch for designating any one of anumber of contacts,

thereon by changing the electrical condition thereof, a senderassociated with said control circuit for variably actuating saiddesignating means, and additionalmeans for said switch for selecting thedesignated contact.

2. In a telephone exchange system, the combination with an automaticswitch having associated contacts, designating means individual to saidswitch for automatically rendering selectable at Will a particularcontact therein by changing the electrical condition thereof, a senderadapted to operate the same, and additional means associated with saidswitch for selecting the particular contact, substantially as set forth.

3. In a telephone exchange system, the combination wlth an automaticswitch having associated contacts, of a control circuit for said switch,of designating means individual to said switch, a sender in said controlcircuit for operating at will said designating means to automaticallyrender a particular contact. in said switch selectable by changing theelectrical condition thereof, and additional means associated with saidswitch for selecting the particular contact, substantially as set forth.

4. In a telephone exchange system, the combination with.an automaticswitch having associated contacts, of means associated with said switchfor selecting said contacts, additional step-by-step means individual to.said switch. for rendering a particular one of said contactsselectableby said selecting means by changing the electrical condition of saidparticular contact, and a sender adapted to operate the same,substantially as set forth. 1

5. In a telephone exchange system, the combination with an automaticswitch having associated contacts, designating means individual to saidswitch for rendering. any one of said contacts selectable by changingthe electrical condition thereof, a control circuit for said switch, asender therein, means associated with said control circuit and operatedby said sender for automatically operating said designating means torender any one of said contacts selectable by said switch, substantiallyas set forth.

- 6. In a telephone exchange system, the combination with an automaticswitch having a bank of contacts, of an auxiliary stepby-step deviceindividual to said switch for rendering a particular contact in saidbank selectable by changing the electrical condition thereof, a senderadapted to operate the same, and additional means associated with saidswitch for thereafter selecting the particular contact, substantially asset forth.

7. In a telephone exchange system, the combination with an automaticswitch having a bank of contacts, an auxiliary stepby-step deviceindividual to said switch for designating any one of said contacts bychanging the electrical condition thereof, a sender for operating saidauxiliary device, additional means associated with said switch forselecting said designated contact after the operation of the auxiliarydevice, substantially as set forth.

8. In a telephone exchange system, the combination with an automaticswitch having a bank of contacts, of an auxiliary stepby-step deviceindividual to said switch, of a control circuit for said switch, asender therein adapted to operate said auxiliary device to designate aparticular contact in said bank by changing the electrical conditionthereof and additional means associated with said switch for selectingthe designated contact, substantially as set forth.

9. In a telephone exchange system, the combination with an automaticswitch having a bank of contacts, of a control circuit extending to saidswitch, a sender therein, of an auxiliary step-by-step device individualto said switch and controlled by said sender for designating aparticular contact in said bank by changing the electrical conditionthereof, and additional means associated with said switch for selectingthe designated contact, substantially as set forth.

10. In a telephone exchange system, the combination with an automaticswitch having a bank of contacts selectable thereby, of a metalliccontrol circuit for said switch, a sender therein, an auxiliarystep-by-step device individual to said switch and controlled by saidsender to designate the particular contact in the bank to be selected bysaid switch by changing the electrical condition of said particularcontact, substantially as set forth.

11. In a telephone exchange system, the combination with an automaticswitch having an associated bank of contacts, of a two conductormetallic circuit for said switch, means individual to said switch andresponsive to makes and breaks in said circuit for rendering aparticular contact in said bank selectable by changing the electricalcondition thereof, additional means associated with said switch forselecting said contact. substantially as set forth.

12. In a telephone exchange system, the combination with a plurality ofcalling and Largest called subscribers lines, means comprising automaticswitches for connectin said lines, a set of step-by-step relaysindividual to each of said automatic switches, impulse sending meansvfor controlling the step-bystep relays, and additional means whereby theautomatic switches assume positions controlled by their respective setsof relays, substantially as set forth.

13. In a telephone exchange system, automatic switches having associatedsets of contacts, sets of step-by-step controlling relays for saidswitches adapted to determine in advance the particular contacts to beselected by said switches, a sender for operating said relays, and meansassociated with said switches for selecting the designated contact,substantially as set forth.

14. In a telephone exchange system, subscribers lines, connective linkstherefor provided with automatic switches, impulse actuated meansassociatedwith said switches, contact banks for said switches, meanscontrolled by said impulse actuated means for variably designatingcontacts in said banks by changing the electrical condition of saidcontacts, and means for causing said switches to move to a positioncorresponding to the designated contact.

15. In a telephone exchange system, subscribers stations and a centralstation and metallic circuits interconnecting them, automatic switchingapparatus at the central station for interconnecting lines, designatingdevices individual'to said switching apparatus, means at eachsubscribers station for varying the flow of current over the two sidesof his line in series to produce roups of impulses varying in numberaccor ing to a predetermined code, said designating devices beingresponsive to said impulses in the metallic circuit to desi nate bychangin the electrical condition thereof the switc contacts to beselected by said switching apparatus whereby said switching ap aratuseffects connectlons corresponding to t ecode changes produced by acalling subscriber, substantially as set forth.

16. In a telephone exchange system, a connector switch, a releasemagnet, a metallic circuit having answering and calling ends,

a relay arranged to be energized by current over the answering end ofsaid metallic circuit, a relay arran ed to be energized by current overthe cal ing end of said metallic circuit, means controlled by both ofsaid relays when denergized to operate said release magnet, and meanscontrolled by only one of said relays when denergized to operate saidrelease magnet.

17. In a telephone exchange system. a calling line, a called line, ametallic circuit having answering and calling ends, means for connectingsaidcalling line to said answering end, a connector switch for con- 180necting said calling end to said called line, means for completing atalking connection between said lines, a relay arranged to be energizedby current over the answering end of said metallic circuit, a relayarranged to be energized by current over the calling end of saidmetallic circuit, a release magnet, a circuit for said magnet completedthrough the armatures and back' contacts of both relays in series beforethe completion of a talking connection between said lines and a circuitfor said magnet'complete through the armature and back contact of onlyone of said relays after the completion of a talking connection betweensaid lines.

18. In a telephone exchange systein, the combination with an automaticswitch having associated test contacts, releasing'means for said switch,a control circuit extending to said automatic switch, means associatedwith said test contacts comprising a relay and a resistance coil havingtheir windings in series, means exercised over said control circuit forshort circuiting said resistance coil through contacts of said relay toeflect the release of the automatic switch, substantially as set forth.

19. In a telephone exchange system, the combination with an automaticswitch having associated test contacts, of releasing means for saidswitch, a control circuit extending to said switch, meanspredeterminedly associated with said contacts having an appreciableresistance, means exercised over said control circuit for diminishingsaid resistance to affect the releasin means of said automatic switchover sai test contacts. substantially as set forth.

20. In a telephone exchange system, subscribers stations and a centralstation, automatic switching mechanism at the central station forinterconnecting said lines, designating devices individual to saidswitching mechanism, a two-conductor control circuit, means associatedwith said control circuit for varying the flow of current over the twosides of said control circuit in series to produce groups of impulsesvarying in number according to a predetermined code, said designatingdevices being responsive to said impulses in'said circuit to designateby changing the electrical condition thereof the switch contacts to beselected by said switching mechanism whereby said switching mechanismeflects connections corresponding to the code which is produced by saidmeans in said control circuit. substantially as set forth.

21, In a telephone exchange system, the combination with automaticswitching mechanism having associated contacts, designating devicesindividual to said switching mechanism, a two-conductor control circuit,sending means associated with said control circuit for varying the flowof current over the two sides of said control circuit in series toproduce groups of impulses varying in number according to apredetermined code, said designating devices being responsive to theimpulses in said control circuit to designate by changing the electricalcondition thereof the contacts to be selected by said switchingmechanism whereby said 'series according to a predetermined code,

said designating devices being responsive to said variation of currentfor rendering selectable certain contacts of said switching mechanism bychanging the electrical condition of said contacts. and means forcausing the automatic switching mechanism to be set upon said contacts,substantially as set forth.

23. In a telephone exchange system, the combination with an automaticswitch. a device individual to said switch for designating thepositionvto be assumed by said switch, electromagnetic motive means forsaid switch, means for operating said designating means step-by-step inaccordance with a predetermined code, and additional electromagneticmeans for disabling said motive means when the automatic switch assumesa position designated by said device, substantially as set forth.

24. In a telephone exchange system, the combination with an automaticswitch having associated contacts, a designating device individual tosaid switch for changing the electrical condition of any of saidcontacts to select the position to be assumed by said switch,electromagnetic motive means for said switch, and a sender for variablyoperating said designating device step by step in advance of said motivemeans.

25. In a telephone exchange system, the combination with an automaticswitch, a designating device individual to said switch, electromagneticmotive means for said switch, means for operating said designatingdevice step-by-step in accordance with a predetermined code,electromagnetic means associated with said switch for disabling themotive means when it assumes a position corresponding to that of thedesignating device in accordance with said code. substantially as setforth.

26. In a telephone exchange system, the combination with an automaticswitch having associated contacts, a designating device individual tosaid switch for changing the ing associated contacts, an auxiliarydevice individual to said switch responsive to current impulsestransmitted according to a predetermined code, self-actingelectromagnetic actuating means for said switch, electromagnetic meanscontrolled by said device for disabling said actuating means when saidswitch engages a contact corresponding to said code, substantially asset forth.

28. In a telephone exchange system, the combination with an automaticswitch, a designating device individual to said switch, said deviceresponsive to current interruptions transmitted in accordance witha-predetermined code, self-acting electromagnetic actuating meansassociated with said switch, electromagnetic nieans controlled by saiddesignating device for disabling said actuating means when the switchassumes a position corresponding to said code, substantially as setforth.

29. In a telephone exchange system, the

combination with a device for producing a predetermined number ofsignals, of an automatic switch provided with a plurality of contacts,an auxiliary designating device individual to said switch and responsiveto said device for rendering any one of said contacts selectable by saidswitch by changing the electrical condition of said contacts, additionalmeans associated with said switch for thereafter selecting contactsrendered selectable by said designating clevic'e, substantiall as setforth.

30. In a telep one exchange system, the combination with a two-motionautomatic switch having associated contacts, an auxiliary deviceindividual to said switch responsive to current impulses transmittedaccording to a predetermined code, self-acting actuating means foroperating said switch in both directions, and means controlled by saidauxiliary device for changing the electrical condition of any of saidcontacts to determine the positions to be assumed by said switch inaccordance with said code.

In testimony whereof I afiix my signature in presence of two witnesses.

JOSEPH L. WRIGHT.

Witnesses:

ANNA MCCUNE, Ana DEHN.

